Former New York City Mayor Michael Bloomberg addresses the United States Conference of Mayors on June 26, 2017 in Florida. (Photo by Joe Raedle/Getty Images)

Update – September 20, 2017: The architects of America’s Pledge Mike Bloomberg and California Governor Jerry Brown officially announced the 2018 Global Climate Action Summit at the 2017 Bloomberg Global Business Forum on Tuesday. The Summit, which will take place in September 2018 in California, will be co-chaired by Bloomberg and Anand Mahindra, CEO of India’s multinational conglomerate Mahindra Group. Reaffirming his previous stance, Bloomberg said that the American people are committed to the Paris goals regardless of President Trump's decision to pull out. Hoping to see some change in Trump's approach to the Paris Agreement, “Imitation is the most serious form of flattery,” the former mayor of NYC said.

On Wednesday billionaire Michael Bloomberg and California Governor Jerry Brown launched America’s Pledge, a new initiative that will report on the individual efforts taken by U.S. states, cities and businesses to drive down greenhouse emissions “consistent with the goals of the Paris Agreement.” The announcement is a repudiation of President Trump’s decision to pull out of the Paris Climate Agreement in June and is meant to show support for the agreement in the U.S.

The Paris Climate Accord, a pact made by nearly 200 countries in 2015, requires countries to scale down their carbon emissions, along with other measures to slow down the human causes of climate change. The reduction, however, has been interpreted as an effort to undermine American businesses and workers by President Trump, whose 2016 presidential campaign promised to revive the dying coal industry. Through the America’s Pledge initiative, Bloomberg and Brown aim to push back Trump’s policies while collaborating with dozens of other groups.

The Paris pact, referred to as “irreversible” during last week’s G20 meeting in Hamburg by the EU, has been ratified by 153 countries and signed by 197. Yet, it has no binding power, and others may be following Trump’s footsteps. “After that step taken by America, the position that we adopt is in the direction of not passing it in parliament,” Turkey’s President Erdogan said during a press conference shortly after the G20 summit. The remaining 18 countries, however, have reinstated their commitment. France’s new Ecology Minister Nicolas Hulot announced on July 6 that the country will stop selling gas and diesel vehicles by 2040 to meet the agreement’s carbon emission standards.

Despite Trump’s refusal to step back, other American leaders are stepping forward.“The American government may have pulled out of the Paris Agreement, but American society remains committed to it – and we will redouble our efforts to achieve its goals,” said Bloomberg in a statement early on Wednesday. Right after Trump’s decision to pull out on June 1, Bloomberg announced he was pledging up to $15 million to the United Nations Framework Convention on Climate Change to compensate for any loss caused by the U.S. policy change. Bloomberg, whose real-time net worth is $50.8 billion according to Forbes, is one of the country’s top donors, having given away more than $4 billion including more than half a billion dollars in 2016. He is also the UN Secretary-General’s Special Envoy for Cities and Climate Change.

Bloomberg and Brown have also commissioned the Rocky Mountain Institute and the World Resources Institute to lead an inclusive analytical effort in support of America’s Pledge, according to the statement released on Wednesday. In November, the two leaders along with others will showcase existing climate commitments of the U.S. subnational at the UN’s 23rd Conference of the Parties to the Framework Convention on Climate Change in Bonn, Germany.

“Today we’re sending a clear message to the world that America’s states, cities and businesses are moving forward with our country’s commitments under the Paris Agreement — with or without Washington,” said Governor Jerry Brown, who was recently named Special Advisor for States and Regions ahead of the UN’s conference. Brown will also host the world’s climate leaders in San Francisco in September 2018 for the Global Climate Action Summit.

America’s Pledge and its efforts to include the U.S. in the international push against climate change have already been noticed. “The effort to aggregate and quantify the actions of subnational authorities and non-Party stakeholders in the United States via ‘America’s Pledge’ is welcome,” United Nations Secretary-General António Guterres said on Wednesday.

E-mail Deniz at dcam@forbes.com or follow on Twitter. If you have a tip, you can reach us confidentially, at tips@forbes.com or via our SecureDrop site.

Deniz Cam is a wealth reporter at Forbes Magazine, where her work includes billionaires’ philanthropy and influence in politics. Born and raised in Istanbul, Deniz graduated from Brown in 2015. After Brown, she worked for Brain World Magazine and then interned at Forbes. In...